Wikipedia:Reference desk/Archives/Science/2022 May 13

= May 13 =

Energy for catabolism/catabolic reactions
Catabolic reactions release energy, but for the catabolic reaction itself to happen, is the energy needed? If yes then from where does it get the energy for catabolism? (Catabolism means that in plants and other organisms). -- Exclusive Editor  Notify Me! 05:41, 13 May 2022 (UTC)
 * Many chemical reactions do require an initial input of energy to happen, but release more than they consume. We have an article about activation energy which is rather good if a bit technical. The most interesting reactions for biology all have some activation barrier, because otherwise they would occur on their own as soon as the products are in contact (and are therefore near-impossible to regulate).
 * Most (all?) metabolic reactions use ATP as the "energy currency", spending it when energy is needed and accumulating it when energy is produced. I expect catabolism is no exception. Tigraan Click here for my talk page ("private" contact) 08:46, 13 May 2022 (UTC)
 * To get started on this, the organism will have to make some enzymes, or at leats get them near the molecules that are to be used. This will take energy. A dead organism may not be able to get started to do this. Graeme Bartlett (talk) 10:51, 13 May 2022 (UTC)
 * The energy needed for catabolism is ATP and it comes from one’s metabolism, from everything one eats... (Source : my cousin, who is veterinarian)2A01:CB0C:38C:9F00:CC4A:2EDC:4951:28BF (talk) 08:56, 18 May 2022 (UTC)

Ring strain in cycloalkanes
At cycloalkane it says that "In cycloalkanes, the carbon atoms are sp3 hybridized, which would imply an ideal tetrahedral bond angle of 109° 28′ whenever possible." It then explains about the conformation of the lower cycloalkanes before saying "After cyclohexane, the molecules are unable to take a structure with no ring strain". Can this be correct? Assuming that all the bonds can rotate freely around their axes(?), intuitively one would visualise it to be increasingly likely that larger rings could be joined up somehow in three dimensions with all the angles correct. Is that really never geometrically possible? 2A00:23C8:7B09:FA00:E139:B276:E11C:BF90 (talk) 08:38, 13 May 2022 (UTC)
 * Although that is possible, there are two other types of strain, tortional strain, where the hydrogen atom bonds repel each other, and steric strain, when atoms are pushed together. A balance takes place that minimises the energy by moving the atoms around. My Organic Chemistry textbook confirms what the article says for up to 14 carbon atoms. 11:36, 13 May 2022 (UTC)
 * Apologies,, our edit conflict seems to have removed your name from your contribution Mike Turnbull (talk) 11:58, 13 May 2022 (UTC)
 * (edit conflict) The best article is probably Strain (chemistry). However, I consulted my venerable fourth-edition copy of Jerry March's "Advanced Organic Chemistry" (ISBN=0471601802, pages 150–164) for a decent account I could trust. Later editions such as the 2006 one no doubt have similar stories. The strain you are referring to is called small-angle strain but strain also arises from nonbonded interactions. In medium-sized rings (7 to 13C) conformations in which the angle strain is minimised create transannular strain or Pitzer strain. At these ring sizes, one or more of these sources of strain must be present. Once ring sizes go above 13 there is little or no strain according to March. The cycloalkane article is, I believe, currently wrong when it says (unsourced) After 14 carbon atoms, sources disagree on what happens to ring strain, some indicating that it increases steadily, others saying that it disappears entirely. I'll change that part and give sources like March to back up the idea that strain tends to zero, provided no-one here mentions a reliable source that says otherwise! Mike Turnbull (talk) 11:52, 13 May 2022 (UTC)
 * 10.1007/s40828-015-0014-0 is useful. I have no idea how reliable that journal is, but that article at least has a lot of refs that could be useful. For example, it notes a general pattern that even-sized rings often have a some well-defined low-energy conformations (after accounting for symmetry) whereas odd-sized rings generally don't (at least some sort of strain in each conformation). And that large rings collapse into a floppy oval with van der Waals effects becoming attractive. And that cycloheptadecane has negative ring-strain. I can't access 10.1007/BF00141578 at the moment, but it discusses the C18, C19, and C20 sizes. DMacks (talk) 12:17, 13 May 2022 (UTC)
 * Yes, thanks,, 10.1007/s40828-015-0014-0 is perfect and is open-access: pdf linked here. The part that points out that being strain-free equates to being able to reach a conformation corresponding to a diamond lattice is particularly pertinent (explaining why cyclohexane is essentially strain-free). I'll use that ref to update cycloalkane. The other article you linked is much older and not so useful, I think. Mike Turnbull (talk) 12:49, 13 May 2022 (UTC)


 * Thanks for the replies; in my reading, the original text gave the impression that "ring strain", in the sentence that I quoted, arose only from angles not being exactly tetrahedral. If there are other forms of "ring strain", or reasons why a ring would not adopt an all-angles-correct conformation even if geometrically possible, then that would explain my puzzle. 2A00:23C8:7B09:FA00:2056:8CA5:3D04:E1C1 (talk) 14:11, 13 May 2022 (UTC)

metal waterbottle
I have a metal waterbottle that I got as tech swag. I don't know if it is lined or unlined, stainless steel, aluminum, or what. Is there a way to tell? A magnet doesn't stick to it, but I think some stainless steels are non magnetic. I left water in it for a fairly long time (probably breeding germs), so I rinsed it out with soapy water and then poured some boiling water into it. It seems like there is some pitting on the bottom, probably not a hazard in and of itself? Thanks for any thoughts. 2601:648:8202:350:0:0:0:738F (talk) 20:58, 13 May 2022 (UTC)


 * 'd be astonished if it wasn't aluminium, the original ones were made by the Swiss firm of Sigg. Alansplodge (talk) 21:10, 13 May 2022 (UTC)
 * It does look like a Sigg bottle (I'm familiar with them), though I figure that can just be a styling nod. Stainless steel bottles are also common, though.  Kleen Canteen is a well known maker of those.  I'll look more closely for markings on the bottle I have.  I suppose it could be a Sigg bottle with customized branding.  Thanks. 2601:648:8202:350:0:0:0:738F (talk) 22:29, 13 May 2022 (UTC)
 * Hi! I would put mix of boiling water and cleaning vinegar (equal parts) and leave it for 30 mins or so then clean it thoroughly with soap after that before using. It should clear out. ~ Nanosci (talk) 14:08, 14 May 2022 (UTC)
 * Thanks, I will give that a try, though I have been using it since the soap and water flush I did a few days ago. Btw I'm fairly sure now that it is not a Sigg(tm) bottle, although it is a "tribute" to one.  It has no markings but has a small sticker on the bottom saying it was made in China.  I have a couple of genuine Sigg bottles stashed away so I can inspect them too.  I guess if I get a little bit creative, I can find a way to measure the density of the metal of this bottle (will require measuring the displacement in a liter or two of water to within a ml or so).  2601:648:8202:350:0:0:0:738F (talk) 06:41, 16 May 2022 (UTC)
 * If you can measure the volume, you can test density. The electrical conductivity is different too, but a bit hard to measure due to surface effects. Magnetic properties may be a bit hard to do without a lab (and you have already established it isn't ferromagnetic). You may be able to measure thermal conductivity (put hot water in, measure how fast it cools) or specific heat (make the bottle warm with hot water, remove the hot water, put a bit of cold water in, shake it and measure the temperature change of the cold water. Make sure the bottle is properly insulated on the outside). You can test the melting point, but that may get destructive (if your bottle melts below 700°C, it was aluminium). Chemical tests (how does it respond to strong acids and bases) are effective, but destructive too. PiusImpavidus (talk) 08:28, 16 May 2022 (UTC)

Searching for "metal identification flowchart" gives some results from the welding community, but they all suggest a spark test (i.e. put a sample to a grinding wheel and look at what the sparks look like). Presumably the OP wants something non-destructive.

Thermal properties are going to be hard to measure - you will at least need to measure the thickness of the walls. If we suppose it’s either (stainless) steel or aluminium, density is clearly the way to go: You won’t get a metrology prize or impress your neighbors with either technique, but it’s good enough to differentiate between aluminium (with a density of 2.7 kg/L) and stainless steel (depends on grade, but likely above 6 kg/L). (Of course, if the bottle is parts plastic and part stainless steel, you might incorrectly guess aluminium.) Tigraan Click here for my talk page ("private" contact) 11:52, 16 May 2022 (UTC)
 * 1) Weigh the empty bottle alone -> $$m_1 = m_{bottle}$$
 * 2) Measure the volume of the bottle.
 * 3) Option 1: put the bottle inside a container, fill it up with water, delicately remove the bottle, and measure how much you need to pour to fill it up again. Assuming you have a measuring cup the last part is easy and precise, but the "delicately remove the bottle" part might be more tricky.
 * 4) Option 2: fill up a container with water, weigh, put the bottle inside and re-fill-up, weigh, the increase in weight is equal to $$m_2=m_{bottle} - m_{water\, displaced} = m_{bottle} - \rho_{water}\times V_{bottle}$$. Therefore the volume of the bottle is $$\frac{m_1-m_2}{\rho_{water}}$$ and its density is $$\rho_{bottle} = \rho_{water} \times \frac{m_1}{m_1-m_2}$$